Ring seals are typically annularly shaped, defining an axially aligned hole for fluid (liquid or gas) passage, two axially opposed end surfaces, a radial inner surface, and a radial outer surface. A simplistic ring seal has planar end surfaces and smooth circular radial inner and outer surfaces that define the inner diameter (ID) and outer diameter (OD) of the ring seal. It is common practice in the industry, however, to utilize seals having different radial cross-sections to obtain varying sealing capabilities for different fluid flow environments.
A commonly used ring seal is circular and has a radial cross-section of a “C” shape. These “C seals” are constructed with the open side of the C construction facing the center of the ring such as is described in U.S. Pat. No. 5,354,072, (“the '072 patent”) or with the open side of the C facing away from the center of two mating surfaces are brought together with the C seal in the middle, where the C seal is compressed with the open side of the C cross-section closing during compression. The ductile properties of the seal permit plastic deformation to occur without damaging the mating surfaces. To increase the elastic recovery of the seal, some C seals are provided with a circular elastic helical spring concentrically located within the center of the seal which also alters the compression resistance and elasticity properties to that desired for particular sealing assemblies. Unfortunately, it is relatively complicated to manufacture a C seal having an internal helical spring resulting in the construction of acceptable seals being typically non-repeatable.
Some C seals are provided with a circular ridge, also referred to in the art as a “delta,” formed on the surfaces that come in contact with the opposed parallel surfaces that are intended to be sealed. These ridges lessen the initial contact area between the seal and the parallel opposing surfaces thereby requiring less load to plastically deform the seal, where the deformation allows the seal to accommodate and seal off minor distortions in the parallel surfaces. Unfortunately, C seals with these circular ridges often form a chamber between the circular ridge and the outer surface of the C seal as the seal is compressed. Though this seal may be leak-proof, or have a leak of a sufficiently low value as to be within tolerances, a “virtual leak” is created if there is a leak between this cylindrical chamber and the interior passage of the seal, thereby permitting gases or liquids to flow slowly there between. Though a leak-proof seal is in effect, testing of the seal may erroneously and undesirably reflect that a leak exists, and this condition is therefore referred to as a “virtual leak.”
Modified C seals are known that include an extension extending above the sealing surface of the seal, for example, as described in U.S. Pat. No. 6,688,608, which is incorporated by reference as though re-written herein in its entirety. Such extensions allow for a reduced load or compression force to be used to initiate plastic deformation of the seal when it is compressed between the flow path's sealing surfaces. One example of such a known seal is illustrated in FIGS. 1 and 2. As shown in the figures, the previous ring seal 1 includes an annularly shaped body element 3 having an axial aligned center hole 4 for permitting the passage of gases or fluids therethrough. Due to the annular construction of the ring seal 1, the ring seal 1 includes a radial inner surface 5, a radial outer surface 6, a first axial end surface 11, and a second axial end surface 17. Each of these surfaces may take any number of configurations. They may be substantially flat and planar, or substantially curved. For example, the radial inner surface 5 includes a flat region 7 and curved regions 9. Similarly, the outer radial surface 6 is shown to include a planar surface and an angled abutment. These surfaces may take other forms.
The known ring seal 1 further includes a plurality of bores 25 which project inwardly from the ring seal's radial outer surface 6 towards the ring seal's center hole 4. The formation of the bores 25 creates a plurality of sidewalls 27 which also extend radially from the ring seal's radial outer surface 6, and axially between the ring seal's axial end surfaces 11 and 17.
The illustrated known ring seal 1 also includes a circular ridge or extension 23, which projects axially from the axial end surfaces 11 and 17. The extension 23 divides the first axial end surface 11 into a first inner axial end surface 13 and a first outer axial end surface 15. Similarly, the extension 23 that projects from the second axial end surface 17 divides that axial end surface into a second inner axial end surface 19 and a second outer axial end surface 21. The inner axial end surfaces 13 and 19 recess inwardly with respect to the outer axial end surfaces 15 and 21 to produce an offset. The thickness of the ring seal 1 as measured at the inner axially end surfaces 13 and 19 is thinner than the thickness of the ring seal 1 as measured at the outer axial end surfaces 15 and 21. A problem with such a ring seal 1 is that the ridge or extension 23 can be damaged during handling or installation. For example, the extension may be nicked or dented. Such damage can result is an inadequate seal.
Still another type of ring seal known in the industry is the “W” seal. Such a sealing system is disclosed, for example, in U.S. Pat. No. 7,140,647 (“the '647 patent”), also herein expressly incorporated by reference, in its entirety. The “W” seal in the '647 patent uses a snap ring situated on the inside of a retaining ring, identified in the patent as a guide, to retain the W-seal in the retainer and to keep the sealing surfaces on the W-seal or gasket protected from scratches. The '647 patent retainer or guide also has a snap ring situated on its outside diameter to keep the retainer engaged in the counterbore, which defines the opposing parallel surfaces to be sealed.
An additional known seal is a “V seal,” which is also circular but instead of having a “C” cross-section, the V seal has a “V” cross-section with the low point of the V constructed to point either inwardly or outwardly towards the center of the seal. Though this construction typically provides for sufficient deformation, the V seal does not typically provide particularly good elastic recovery or repeatability because the point of the V seal forms a stress raiser that concentrates the compression loads and makes the seal prone to failure upon repeated compressions and decompressions of the seal.
Additional seals in the art include “Z seals” and simple “O rings.” Each of these seals also suffer various disadvantages.